Chevrotain

EMPTY_ALT

• EMPTY_ALT<T>(value?: T): function

• convenience used to express an empty alternative in an OR (alternation). can be used to more clearly describe the intent in a case of empty alternation.

  for example:

  1. without using EMPTY_ALT:

     this.OR([ {ALT: () => {

     this.CONSUME1(OneTok)
     return "1"
     

     }}, {ALT: () => {

     this.CONSUME1(TwoTok)
     return "2"
     

     }}, {ALT: () => { // implicitly empty because there are no invoked grammar rules (OR/MANY/CONSUME...) inside this alternative.

     return "666"
     

     }}, ])

  • 1. using EMPTY_ALT:

       this.OR([ {ALT: () => { this.CONSUME1(OneTok) return "1" }}, {ALT: () => { this.CONSUME1(TwoTok) return "2" }}, {ALT: EMPTY_ALT("666")}, // explicitly empty, clearer intent ])

  Type parameters

  • T

  Parameters

  • Default value value: T = undefined

  Returns function

  • • (): T

    • Returns T